Scientific Method —

Stealthy strides are less efficient: how cats walk

A new study from Duke University shows that the cat's stealthy prowl is …

Cats and dogs, dogs and cats. Mankind's best friends can be a little polarizing, with cat people not really 'getting' dogs and vice versa. Canid connoisseurs point to the loyalty and utility of dogs (fetching stuff, smelling things, rounding up errant sheep), and felid fanatics claim as virtue such traits as pest control, self-cleaning, and their use as furry hot water bottles on cold mornings. A paper in PLoS ONE examines a rather interesting difference between these two species, one that stems from evolutionary pressure over the ages.

The study, from a group of researchers at Duke University, examines the way in which cats walk. That might sound like a pretty simple thing, and one that had already been well characterized but, as it turns out, that's not the case.

Dogs, and other animals that have evolved to be good at walking long distances at a steady pace, are really quite efficient in their movement. Dogs walk with a rather stiff-legged gait, and this helps save energy by creating a pendulum-like center of mass that stores kinetic energy as potential gravitational energy. The dogs get that back as kinetic energy as they move. This recovers around 70 percent of the kinetic energy expended, theoretically saving metabolic energy (although not much work has been done to confirm this last bit).

Cats, on the other hand, aren't specialized for walking long distances. Instead, as most cat owners will know, they make use of a range of walking motions, from a stiff stance similar to the dog to the crouched stalk that usually means someone or something will be getting a surprise clawing. The need to be able to stalk prey with stealth means that, when cats utilize this gait, they recover almost no kinetic energy at all.

According to Daniel Schmitt, one of the authors, "the movements of their front and back ends cancel each other out." He added "If they're creeping, they're going to put this foot down, and then that foot down and then that one in an even fashion. We think it has to do with stability and caution."

Even when trotting along with a gait similar to that of dogs, the best that cats could manage as far as energy recovery was a measly 37 percent, suggesting that evolutionary pressure towards an efficient gait was much stronger in dogs than cats. As a cat owner, this isn't very surprising, as I'm quite positive that any cat that has a need to get somewhere far away is more than capable of 'persuading' someone else to pick them up and do the hard work for them...